Lead storage batteries are widely known. Such lead storage batteries generally include a battery casing enclosing electrode plates and terminal posts projecting through a casing top wall that closes the top of the battery casing. A lead bushing for enclosing the terminal posts is generally mounted on the battery casing top wall.
FIG. 7 shows an example of a conventional lead bushing 1 including a tube 2 and a plurality of ring protrusions 4 around the lower end of tube 2 which is hollow and has an opening 9 in the upper tube end. The lower end of the tube 2 is also open.
FIG. 8 shows the lead bushing 1 shown in FIG. 7 when it is mounted in a battery casing top wall 6 of a lead storage battery. The battery casing top wall 6 has a terminal socket 6a in which the lead bushing 1 is inserted. The plurality of ring protrusions 4 on the outer periphery of the lead bushing 1 effectively cooperate with respective radially inwardly facing ring projections in the terminal socket 6a for preventing leakage of electrolyte. A terminal post 7 is inserted into the lead bushing 1 and the upper ends of the terminal post 7 and lead bushing 1 are electrically connected by a welded portion 2a.
FIG. 9 shows the step of welding the lead bushing 1 to the terminal post 7. A jig 10 required for the welding step is placed around the outer periphery of the lead bushing 1. Then, the upper ends of the terminal post 7 and of the lead bushing 1 are welded together by a burner 11 or the like.
However, lead storage batteries have different sizes and a large lead storage battery with large terminal posts requires large diameter lead bushings 1. The welding is performed manually which is not efficient. In addition, welding as such is difficult. Furthermore, the above mentioned welding can disadvantageously produce an unexpected alloy in the welded portion 2a, which alloy may cause a corrosion problem or the like.